The present invention relates to a new and improved luminaire and more particularly, to a new and improved luminaire including a double acting reflector system and a clear, nonprismatic lens assembly. With this reflector system and lens assembly, the luninaire projects light downwardly in a generally rectangular pattern with a sharp horizontal cutoff.
Many buildings and facilities employ protective security lighting to protect the premises. These buildings and facilities have open access to the public and as a result, can be vandalized or entered by intruders. In many cases, the protecive security lighting system constitutes the only security system.
Effective protective security lighting systems discourage or deter intruder attempts by making the intruder believe that detection by building occupants, passing pedestrians or police, or a regular night watchman will be inevitable, if entry into the area occurs. These systems should offer their users reliability, and failure of a single lamp or lamps should not create a large dark area vulnerable to intrusion. Consequently, well defined side light from each luminaire in the lighting system is desirable.
Although high visibility is desired, protective lighting should not create glare or spill light. It is usually necessary in protective lighting to avoid light pollution since zoning laws have become so mixed that in many areas industrial, commercial and residential districts often overlap or closely adjoin. Light spilling over into a residential section from protective lighting can be both annoying and disruptive. Consequently, many cities have adopted ordinances designed to reduce light pollution.
One desirable way to provide protective lighting while avoiding light pollution is the use of wall mounted luminaires which provide an asymmetrical generally rectangular light pattern normally classified as an IES/ANSI type III distribution. Since with this type of lighting, glare or light spilling increases as the vertical height of the luminaire and the vertical angle of flux emission increases, control of the candlepower distribution is very desirable. Such control may be accomplished with cutoff techniques.
Light distribution in luminaires is often accomplished through the use of a prismatic lens. An example of this use of a prismatic lens is disclosed in U.S. Pat. No. 4,398,239. Prismatic lenses are not the most effective way to control light distribution, since these lenses tend to scatter light randomly, thereby sending light into unneeded or unwanted areas and resulting in an uneven light pattern. To overcome the inefficienty of scattered light and to obtain the desired light level in the desired area, a larger than necessary amount of energy is required and used by these luminaires.
Additional energy is lost in luminaires using prismatic lenses, since the prims may reflect almost onehalf of the light back into the fixture. Much of this light is lost in the fixture in the form of heat.